Method for irreversibly transferring a diffraction grating, transfer film and device therefor

Abstract

The present invention relates to a procedure for irreversibly transferring a diffraction grating, such as a stamped hologram, onto a substrate, such as a document or a product to be secured, which procedure consists of preparing a transfer film consisting of a supporting film substrate that carries at least one layer formed by a protective film overlay, a metallized or transparent reflective layer that carries the stamped optical image, and a layer of activatable adhesive. The procedure consists of superimposing the transfer film prepared in the above-described manner and of applying pressure with a transfer tool. The stage consisting of the preparation of the transfer film consists of depositing, onto a supporting film substrate whose dimensions are greater than those of the element to be transferred, at least one optical element whose dimensions correspond exactly to those of the element to be transferred onto the substrate. The transfer tool acts on a portion of the transfer film whose dimensions are greater than those of the surface that corresponds to the element to be transferred. The invention also relates to a transfer film and to a tool for the implementation of the procedure.

I claim: 
     
       1. A method for permanently laminating a diffraction grating onto a substrate, comprising the steps of: (a) superimposing a transfer film over the substrate, whereby the transfer film comprises an assembly of a supporting film substrate, at least one protective film overlay, a reflective layer with the diffraction grating, and a layer of adhesive, wherein whereby the layer of adhesive is comprised of an adhesive which abuts the substrate;   (b) feeding the superimposed transfer film and substrate into a transfer tool comprised of a pair of pressure and heat-applying rollers positioned on opposing sides of the superimposed transfer film and substrate;   (c) concurrently applying pressure and heat by way of the pair of the rollers to the superimposed transfer film and substrate to permanently join the superimposed transfer film and substrate; and   (d) collecting the superimposed transfer film and substrate.   
     
     
       2. The method of claim 1, whereby the adhesive is a heat-activatable adhesive. 
     
     
       3. The method of claim 1, whereby the adhesive is a permanent adhesive and the layer of adhesive is protected by a peelable film that is removed prior to superimposing the transfer film over the substrate. 
     
     
       4. The method of claim 1, whereby the adhesive is reactivatable by ultraviolet radiation and the layer of adhesive is activated by irradiation with ultraviolet radiation prior to superimposing the transfer film over the substrate. 
     
     
       5. The method of claim 1, whereby the transfer film is superimposed over a portion of the substrate carrying a photograph. 
     
     
       6. The method of claim 1, whereby the diffraction grating is a stamped hologram. 
     
     
       7. The method of claim 1, whereby a photograph, separate from the substrate, is placed between the substrate and transfer film, such that step (b) permanently seals the photograph between the superimposed transfer film and substrate. 
     
     
       8. The method of claim 1, whereby the dimensions of the supporting film substrate are greater than the dimension of the diffraction grating. 
     
     
       9. The method of claim 1, whereby the supporting film substrate is greater than 10 micros and preferably between 25 microns and 100 microns. 
     
     
       10. A method for permanently laminating a diffraction grating into a substrate, comprising the steps of: (a) irradiating by ultraviolet light a transfer film over the substrate, whereby the transfer film comprises an assembly of a supporting film substrate, at least one protective film overlay, a reflective layer with a diffraction grating, and a layer of adhesive, whereby the layer of adhesive is comprised of an adhesive reactivatable by ultraviolet light which abuts the substrate;   (b) feeding the superimposed transfer film and substrate into a transfer tool to permanently join the transfer film and the substrate; and   (c) collecting the superimposed transfer film and substrate.   
     
     
       11. The method of claim 10, whereby the transfer film is superimposed over a portion of the substrate carrying a photograph. 
     
     
       12. The method of claim 10, whereby the diffraction grating is a stamped hologram. 
     
     
       13. The method of claim 10, whereby a photograph, separate from the substrate, is placed between the substrate and transfer film, such that step (b) permanently seals the photograph between the superimposed transfer film and substrate.